1. Field of the Disclosure
The disclosure generally relates to the field of device authentication, more particularly, for example, to systems and methods in which a multimedia source device communicates with a multimedia sink device (such as a display, or signal distributor), wherein the multimedia source device confirms the identity of the sink device and confirms its trustworthiness through a trust authority.
2. General Background
Digital audio/video source devices (e.g., item 140 shown in FIG. 1), such as set top boxes, DVD players, Blu-ray players, media servers and video game consoles, typically connect to a compatible digital sink device (herein referred to as a “display device,” such as item 150 shown in FIG. 1) such as an A/V receiver, digital television, digital projector or monitor, via a digital audio/video interface that transmits digital data from the source device to the output device. Commonly used digital audio/video interfaces include HDMI (High-Definition Multimedia Interface) and DVI (Digital Visual Interface). FIG. 1 provides an example of an HDMI-based digital audio/video interface.
As shown in FIG. 1, the HDMI interface (100) can be described as being formed of three communication channels, including a transition minimized differential signaling (TMDS) channel (110), a display data channel (DDC) (120), and a consumer electronics control (CEC) channel (130). In addition, audio/video (A/V) data, information on an apparatus, and control commands may be transmitted and received through the HDMI. The TMDS channel is typically used for transmitting and receiving video signals and audio signals. The DDC is a data communication standard between a source device and a display device, defined by VESA, which is an international standards-setting organization. When booting a system, the output apparatus realizes an optimum image by referring to information about the monitor. In general, the source device transmits optimum video signals and audio signals with reference to enhanced extended display identification data (E-EDID) of the display device. The CEC channel is an additional protocol for performing high-level control functions in the HDMI interface.
As is typical with digital audio/video interfaces, “in-band” data, i.e., data that is contained within the audio/video data stream, and “out-of-band” data, i.e., data that is not contained within the audio/video data stream, are used to provide an essentially self-configuring link between the digital audio/video source device and a compatible digital output device. Thus, “out-of-band” data is communicated back to the source device from the display device via the interface, allowing for two-way communication between the source and display device.
In addition to sending in-band audio/video data to the digital audio/video display device, most digital sources also send data to the display device regarding the A/V data format of the audio/video source through a data block sometimes referred to as an “InfoFrame.” In the case of HDMI, this InfoFrame is typically compliant with one or more revisions of EIA/CEA-861, an industry standard.
The display device in most digital audio/video interfaces typically allows the device's EDID (Extended Display Identification Data) information to be read back by the source device, which is a data structure provided by a digital display to describe its capabilities to a source (e.g., graphics card, set-top box). For instance, the EDID enables a source device to know the make and model of the projector to which it is connected, as well as the capabilities of that projector.
Although the EDID of a display device provides for some level of security by allowing a source device to determine the type and capability of such a display device, as currently implemented by most consumer electronics digital display devices, the data block on an EDID itself is not secure, and may be subject to spoofing or may otherwise become compromised. Although HDCP (High-bandwidth Digital Content Protection) protects audio/video data being transmitted via HDMI by obfuscating the data, in the event that the security of the HDCP scheme is compromised, the potential for spoofing of the EDID allows for a potential breach in the security of the system.
It is desirable to address the limitations in the art. For example, it may be desirable to provide a method or system for using a digital audio/video source device, using common digital audio/video interfaces, such as HDMI or DVI, to verify that a digital audio/video display device is a genuine, trustworthy device without relying solely on the EDID of the display device to confirm the identity and security of such a display device. Furthermore, it is desirable to provide a method that can be used to retrofit existing deployed products with these authentication capabilities.